Road Tuning: Tuning Steady State On The Road
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Tuning Steady State On The Road
07.21
| 00:00 | - Since the engine's performance is much more critical of air fuel ratio than ignition timing, we always want to start with the fuel table. |
| 00:08 | The numbers we entered into the ignition map during the table configuration should be adequate for now to have the engine running safely without detonation, but while completing the fuel tuning, you should still use knock detection equipment to listen for knock. |
| 00:23 | The aim with steady state fuel tuning is to adjust the numbers in the main fuel table to achieve our desired air fuel ratio. |
| 00:31 | It sounds simple, and it is, but there are a few tricks that we're going to discuss that will make the job easier and give you a more accurate result faster. |
| 00:42 | To make the tuning changes, we want to drive the car on the road and visit each site in the fuel table. |
| 00:48 | Since we're starting from a blank fuel table, we want to start with as little RPM as possible and as little throttle opening. |
| 00:56 | We're going to use the left foot braking technique to help apply load so we can control where in the fuel map we're accessing. |
| 01:04 | I like to use second or third gear so that the car isn't going too fast. |
| 01:09 | There is a trade off here though, because the lower the gear we use, the more the engine torque is multiplied. |
| 01:16 | This means we need to apply more brake pressure to control the engine load and this can result in too much heat in the brakes. |
| 01:24 | With very powerful cars, you can find the car will actually start wheel spinning in very low gears. |
| 01:31 | I'm going to start by driving the car at 1500 RPM and reduce the throttle to access the lowest cell in the 1500 RPM column we can reach. |
| 01:41 | If we back off the throttle too far, the engine will just slow down, since the car needs some amount of torque to keep driving at a constant speed. |
| 01:50 | Now we should be ready to make some tuning changes. |
| 01:54 | Before we do though, we want to make sure that engine is running in the center of the cell we're about to tune. |
| 02:01 | The G4 Plus has a nice target box, which shows you how close you are to the center of the cell where the cursor is currently in. |
| 02:08 | You can adjust the brake pressure, as well as the throttle position until you are centered in the cell, and now you can make changes. |
| 02:17 | What we want to do is check the measured air fuel ratio and see how it compares to our target. |
| 02:24 | If there's a discrepancy, we can use the shift plus Q, or shift plus A keys to increase or reduce the fuel delivery to get the AFR right. |
| 02:34 | If we find we're a long way from our target, you may need to stop and make some coarser adjustments to get the entire 1500 RPM row closer before you start fine tuning. |
| 02:45 | In this case, I'd highlight the entire 1500 RPM column and add or subtract fuel as required. |
| 02:52 | Once we have tuned the first cell, we want to increase the load by applying more throttle until we're in the next load zone. |
| 02:59 | Before we do this though, we can save time by copying the number from the cell we just tuned and moving it up into the next cell. |
| 03:06 | Since air flow will generally increase as we open the throttle, we can assume that the number we will need in the next cell is going to be close to that of the cell we've just tuned, and perhaps a little larger. |
| 03:18 | Copying the number ahead like this means we are already going to be close when we get into the next cell. |
| 03:24 | This reduces our tuning time and also means there's less chance of the engine running lean while we get the tune correct. |
| 03:31 | From here, the job is just a case of repeating the process of tuning the cell, increasing the load and repeating again until we reach full throttle. |
| 03:40 | At this point, that particular column of the fuel map is tuned completely and we can increase RPM to the next RPM range and repeat again. |
| 03:50 | Before we do this though, we want to copy the numbers from the 1500 RPM column we just tuned and paste them into the 2000 RPM column. |
| 03:59 | This means the numbers we're going to use are going to be close in this RPM range when we start tuning. |
| 04:06 | Since this steady state tuning can be quite hard on the brakes, I tend to tune a column, or in a more powerful car, even just part of a column before easing off the brakes and spending some time allowing them to cool before tuning the next column. |
| 04:21 | Since we can expect the engine's VE to increase as we move from 1500 to 2000 RPM, the numbers are likely to be higher than what we had in the 1500 RPM column and there are a couple of time saving tricks here to help you. |
| 04:36 | First of all, before tuning the 2000 RPM column, I'll usually add 5% to the entire column. |
| 04:43 | This is just a guess at how much I expect the air flow to increase at this RPM range. |
| 04:48 | We can now start running the engine at 2000 RPM and again, we want to start with as little throttle as possible to achieve minimum load. |
| 04:56 | At this point, we check the AFR and see how it compares to our target. |
| 05:01 | All going well, we should already be very close. |
| 05:04 | If there's a difference, we can use the shift plus Q, or the shift plus A keys to add and subtract fuel. |
| 05:11 | This time though, we'll start by applying the change to the entire column. |
| 05:15 | This will get our entire column closer to target before we start tuning individual sites. |
| 05:21 | Now we just repeat the earlier process and tune each cell, gradually increasing the load until we reach full throttle. |
| 05:29 | This is the process that we use and repeat as we increase the RPM. |
| 05:33 | You will start to see a pattern emerge of what the fuel table needs to look like and what we're trying to achieve. |
| 05:40 | At higher RPM, this process can put a lot of stress on the engine and the brakes might not be able to hold the engine power. |
| 05:48 | The reality is that nobody ever really drives their car at part throttle at six and a half thousand RPM for extended periods of time though. |
| 05:56 | What I mean by this is that there are certain parts of the fuel map that we don't need to be quite so accurate about. |
| 06:02 | My rule of thumb is to use the steady state tuning process up to around two-thirds of the engine rev limit. |
| 06:08 | In our example, I'm going to tune to 5000 RPM. |
| 06:13 | From here, we can simply copy the table numbers across to the right to fill out the remaining cells. |
| 06:19 | What we can do then is check each of the higher RPM rows briefly and adjust the entire column up or down until our mixtures are about right. |
| 06:28 | I do this by highlighting the entire column before I start tuning. |
| 06:33 | I then bring the engine up to the required speed at moderate throttle and watch the air fuel ratio. |
| 06:38 | I'll then increase or decrease the entire column until the mixture's where I want it. |
| 06:44 | Again, since the engine will only operate here during transient periods, we don't need to be super accurate, and I prefer to have the mixture a little richer for safety. |
| 06:54 | We can then repeat the process for the rest of the columns on the map. |
| 06:59 | The side benefit is that this will have the full power tune closer when it comes time to do the full power ramp runs. |
| 07:07 | So, at the end of this module, you should know how to control the engine on the road, to tune the fuel map in steady state, and how to adjust the fuel map to achieve your target air fuel ratio. |
